Effects of processing parameters on physical properties of reversible thermochromic microcapsules

Polyethylene/ethyl cellulose (PE/EC) thermochromic microcapsules were prepared by the way of oil phase separation and encapsulation of thermochromatic material (CoCl₂·6H₂O) with large molecule material when ethyl cellulose (EC) and polyethylene (PE), CoCl₃·6H₃O and Span80 were used as the shell material, the core material and the solvent and emulsifier, respectively. Effects of the processing parameters such as the content of PE/EC and span80, the agitation rate, the time of phase separation and content of cyclohexane on shape of microcapsule and encapsulation rate were investigated. The results show that the processing parameters hardly affect the temperature of the change of the color. But the encapsulation rate of reversible thermochromic microcapsule is increased with lasting of the time of phase separation and it exhibits a maximum value with increasing of the stirring speed. The microcapsules were also characterized by scanning electron microscopy (SEM) and optical photographic microscopy (OM), indicating that the optimum conditions of preparing the microcapsules are the mass ratio of core material to shell material of 1:1 and the time of phase separation of 3 h-4 h and agitation rate of 900 r/min. The thermochromic microcapsules exhibit that the properties of reversible thermochromic materials such as the sensitivity of color transition, the adaptability for environment and the compatibility with polymer were greatly improved and thus they will have a good prospect of applications.